giflib: define prefix and libversion also when building (#25263)

var/spack/repos/builtin/packages/giflib/package.py

@@ -24,14 +24,24 @@ class Giflib(MakefilePackage, SourceforgePackage):
 
     patch('bsd-head.patch')
 
+    def prefix_and_libversion_args(self):
+        args = []
+        if self.spec.satisfies('@5.2.0:'):
+            args.extend([
+                'PREFIX={0}'.format(self.spec.prefix),
+                'LIBMAJOR={0}'.format(self.spec.version.up_to(1)),
+                'LIBVER={0}'.format(self.spec.version)
+            ])
+        return args
+
+    @property
+    def build_targets(self):
+        targets = ['all'] + self.prefix_and_libversion_args()
+        return targets
+
     @property
     def install_targets(self):
-        targets = ['install']
-        if self.spec.satisfies('@5.2.0:'):
-            targets.append('PREFIX={0}'.format(self.spec.prefix))
-            targets.append('LIBMAJOR={0}'.format(self.spec.version.up_to(1)))
-            targets.append('LIBVER={0}'.format(self.spec.version))
-
+        targets = ['install'] + self.prefix_and_libversion_args()
         return targets
 
     def check(self):